U.S. patent application number 10/750272 was filed with the patent office on 2005-02-03 for three ply bolted temporary road mats and apparatus for manufacturing same.
Invention is credited to Harrison, Ronald.
Application Number | 20050022363 10/750272 |
Document ID | / |
Family ID | 32965356 |
Filed Date | 2005-02-03 |
United States Patent
Application |
20050022363 |
Kind Code |
A1 |
Harrison, Ronald |
February 3, 2005 |
Three ply bolted temporary road mats and apparatus for
manufacturing same
Abstract
An apparatus for making temporary road mats characterized by
multiple layers of mutually perpendicular elongated timbers having
an array of vertical intersections aligned in lateral rows. The
apparatus includes a gang drill that moves relative to a roughly
assembled mat for sequentially drilling the lateral rows of
intersections.
Inventors: |
Harrison, Ronald; (Plymouth,
NC) |
Correspondence
Address: |
MILLS LAW FIRM, PLLC
P.O BOX 1245
Cary
NC
27512-1245
US
|
Family ID: |
32965356 |
Appl. No.: |
10/750272 |
Filed: |
January 2, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10750272 |
Jan 2, 2004 |
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10407992 |
Apr 7, 2003 |
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6745452 |
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Current U.S.
Class: |
29/525.01 ;
29/26A; 408/49 |
Current CPC
Class: |
Y10T 29/49947 20150115;
Y10T 408/35 20150115; Y10T 29/49948 20150115; Y10T 408/3811
20150115; Y10T 408/3828 20150115; Y10T 408/385 20150115; E01C 9/086
20130101; B27C 3/00 20130101; Y10T 29/53978 20150115; Y10T 29/5136
20150115; B23B 39/161 20130101; Y10T 29/5107 20150115; B27B 5/04
20130101; B27M 3/0046 20130101; Y10T 29/5124 20150115 |
Class at
Publication: |
029/525.01 ;
029/026.00A; 408/049 |
International
Class: |
B23P 011/00; B23B
039/16 |
Claims
What is claimed:
1. An apparatus for making temporary road mats consisting of at
least an upper layer and a lower layer, one of said layers
including laterally spaced, longitudinally extending timbers,
another of said layers including longitudinally spaced, laterally
extending timers, said timbers overlying at an array of vertical
intersections comprised of longitudinally spaced lateral rows, said
apparatus comprising: a frame member; an assembly support carried
on said frame member on which said timbers may be roughly assembled
thereon into said layers with said intersections; a gang drill
assembly supported on said frame member, said gang drill assembly
carrying a plurality of drill units above said layers for drilling
said lateral rows of intersections; means operatively associated
with said frame member and said drill units for selectively
aligning said drill units with said lateral rows and for downwardly
for moving said drill units to form aligned holes through said
timbers at said intersections subsequent to which bolts are
inserted into said holes above said timbers and fasteners are
connected with said bolts below said timbers resulting in a bolted
assembled mat.
2. The apparatus as recited in claim 1 wherein said gang drill
assembly is selectively longitudinally moveable with respect to
said frame member.
3. The apparatus as recited in claim 1 wherein said gang drill
assembly is stationary and said assembly table is longitudinally
moveable with respect to said drill units.
4. The apparatus as recited in claim 3 including indexing conveyor
means for longitudinally moving said assembly table to successively
align said lateral rows of intersections with said drill units for
drilling said through holes.
5. The apparatus as recited in claim 4 including an end conveyor
and trimming station at one end of said assembly table for cutting
rough timber to length for longitudinally extending timbers and for
presenting the same for assembly.
6. The apparatus as recited in claim 5 including a first side
conveyor and trimming station at one side of said assembly table
for cutting rough timber to length for said laterally extending
timbers and for presenting the same for assembly.
7. The apparatus as recited in claim 6 wherein said mat includes a
top and bottom layer of laterally extending timbers, said first
side conveyor and trimming station cutting said rough timber to
length for said bottom layer, and a second side conveyor and
trimming station on the other side of said assembly table for
cutting rough timber to length for said laterally extending timber
of said top layer and for presenting the same for assembly.
8. The apparatus as recited in claim 1 wherein said drill units
include a first bit section for forming said through holes and a
second bit section for forming counterbores in said upper layer of
timbers.
9. The apparatus as recited in claim 8 including second drill units
for forming counterbores in said lower layer of timbers.
10. The apparatus as recited in claim 1 including plate means
overlying said lateral rows of drilled holes after insertion of
said bolts through said through holes to maintain the positions
thereof during said fastening.
11. A temporary road mat made with the apparatus as recited in
claim 1.
12. A method of assembling temporary road surfaces having a least
three mutually perpendicular layers of elongated members consisting
of an upper layer, a middle layer and a bottom layer, the upper
layer and lower layer consisting of timbers vertically aligned in
one direction and the middle layer consisting of timbers aligned
transverse to said upper layer and said middle layer whereby the
layers overlap at lateral rows of vertical intersections, said
method comprising the steps of: providing an assembly platform
aligned in relation to a longitudinal path; orienting said bottom
layer on said platform; transversely orienting said middle layer on
said bottom layer; orienting said top layer on said middle layer
parallel to said bottom layer thereby establishing a roughly
assembled mat wherein the layers vertically overlap at lateral rows
and longitudinal columns of intersections; providing a drill
assembly including a plurality of drilling units aligned for
concurrently drilling through holes in unison through intersections
in a said lateral rows; serially indexing the roughly assembled mat
with respect to said drilling units; drilling said through holes
through each row of intersection until all required holes in said
mat are completed; and inserting bolts through each row of drilled
holes following the drilling thereof; and fastening nuts to the
inserted bolts thereby compressively clamping the layers together
at said intersections.
13. The method as recited in claim 12 wherein said serially
indexing is provided by moving the drilling units with respect to
said roughly assembled mat.
14. The method as recited in claim 13 wherein said serially
indexing is provided by moving the roughly assembled mat with
respect to fixedly longitudinally located drilling units.
15. A temporary road mat made in accordance with the method recited
in claim 12.
16. A bolted three ply temporary road mat comprising; a bottom
layer of elongated timbers aligned in parallel rows in a first
direction; a middle layer of elongated timbers aligned in parallel
rows on said bottom layer extending to a second direction
transverse to said first direction; a top layer of elongated
timbers aligned in parallel rows on said middle layer and
vertically aligned with said timbers of said bottom layer whereby
said timbers of said layer overlie at an array of vertically
aligned intersecting surfaces; through hole formed through said
timbers at said intersecting surfaces; and bolts having threaded
shanks extending through said through holes with heads engaging the
upper surface of said timbers of said top layer; and nuts threaded
on said shanks and compressively engaging the lower surface of said
timbers of said bottom layer thereby forming a bolted composite
assembly of timbers.
Description
RELATED APPLICATION
[0001] This application is a continuation-in-part application of
U.S. Ser. No. 10/407,992 filed on Apr. 4, 2003 in the name of
Ronald Harrison and entitled "Apparatus for Assembling Temporary
Road Mats".
FIELD OF THE INVENTION
[0002] The present invention relates to temporary road surfaces
and, in particular, to apparatus for manufacturing and assembling
three ply temporary road mats.
BACKGROUND OF THE INVENTION
[0003] Temporary road mats are used extensively to allow vehicles
and equipment to reach locations not serviced by permanent roads,
particularly under conditions where ground surface would not
support the traffic or where the temporary nature of use does not
warrant the time and expense of a permanent road. The mats are
generally constructed in multiple layers of heavy wood timbers in
crisscrossing layers. The mats may also be provided with
interlocking joints for connecting with adjacent mats as disclosed
in U.S. Pat. No. 4,462,712 to Penland; U.S. Pat. No. 5,032,037 to
Phillips et al.; and U.S. Pat. No. 4,889,444 to Pouyer. Commonly,
each layer is nailed to the underlying layer. The final layer is
fastened with an extended length nail having a protruding tip that
crimped over to secure the assembly as disclosed in U.S. Pat. No.
5,234,204 to Hunt. The manual assembly, even with air powered
nailing guns in time consuming and tiring and prone to
misalignments. For heavy duty applications, three ply mats are
employed. Initially, two layers are nailed as a subunit, with the
third layer nailed thereto in a separate assembly sequence. This
type of nailed construction provides limited torsional and bending
strength, resulting loosening of the nailed joints and timber
breakage. Replacing a damage timber requires time consuming removal
of all overlying timbers. The entire length of timber must be
replaced inasmuch as limited compression and shear strength
precludes splicing with shorter lengths. Where the nail loosening
occurs at the intermediate layer, supplemental nailing from both
the top and bottom surfaces may be required to regain suitable
strength at the joint. Such supplemental nailing can also splinter
the timber resulting in a complete loss of nail holding
strength.
[0004] Various assembly devices have been proposed for more
accurately aligning the timber layers prior to nailing. U.S. Pat.
No. 4,922,598 to Pouyer discloses an assembly table having an array
of alignment stops for assisting positioning the timbers prior to
nailing. U.S. Pat. No. 5,234204 to Hunt, referenced above,
discloses a dual stage assembly table facilitating nailing on
opposite sides of the mat. Crimped extended length nails are used
on the final layer to resist a lifting of the nail heads that can
damage vehicle tires.
[0005] The nailing of the timbers also precludes convenient repair
and replacement of damaged timbers. Typically, the mat must be
substantially disassembled to access and replace damaged members.
Bolted constructions have been suggested in the art, however, such
mats are not known to be commercially available. Therein, holes are
drilled at the intersections of the crossed timbers for receiving
threaded fasteners. The resulting construction provides a smooth
upper surface free of protruding nail heads. When replacement of a
member is required, only the fasteners in the affected area need to
be removed to allow substitution. Notwithstanding the advantages of
the bolted construction, production rates, even with fixtures and
assembly tables, have been limited by the cycle times of the
serially required operations.
[0006] Moreover, three ply mats have not been successfully
produced. The cumulative tolerances in the hole arrays for the
three layers present's extreme alignment problems for assembly.
Approaches increasing the clearances between the holes and bolt
shanks result in a loss of lateral structural stability. Leveraging
the boards to align the holes for assembly results in a stressed
assembly condition that can result in timber fracture and surface
warping.
[0007] Accordingly, a need continues to exist for three ply bolted
temporary road mats that may be assembled accurately under low
stress conditions.
BRIEF SUMMARY OF THE INVENTION
[0008] The present invention provides an improved method for making
bolted three ply temporary road mats wherein fastener holes are
drilled concurrently by a gang drill apparatus into the freely
assembled mat, the apparatus and mat indexed to successive
positions for drilling while the preceding rows are fastened by
carriage bolts, continuing until the mat is fully assembled.
Resultantly, the completed mats can use fastener holes having close
sliding fits with the bolts providing increased bilateral
stability. Moreover, the fasteners are connected with only
compressive forces substantially reducing assembly stresses on the
timbers.
[0009] In one aspect of the invention, a mat assembly line includes
a pair of in-line, phase opposed multilevel assembly tables
supplied with precut timbers from conveyor systems including a
trimming station. The precut timbers are oriented into multiple
layers of mutually perpendicular timbers atop the table. A mobile
gang drill carrying a plurality of drill heads travels along rails
at the sides the assembly tables and sequentially drills through
holes at each lateral row of timber intersections. Carriage bolts
are inserted downwardly through the drilled holes as completed. At
lower bays beneath the assembly tables, nuts are assembled on the
bolts to provide a unitized assembly. During the drilling at the
first table, another mat is assembled at the other table. Following
completion at the first table the gang drill indexes to the second
table and performs the drilling sequence thereat, while the bolts
are fastened at the first table. The gang drill alternates between
the tables, with upper and lower crews transferring between tables
for continuity and efficiency.
[0010] In another aspect of the invention, there is provided a mat
assembly line wherein an indexing conveyor is supplied with precut
timbers from conveyor systems including trimming stations. The
precut timbers are oriented into multiple layers of mutually
perpendicular timbers atop the table. The indexing conveyor shifts
the timber stack to a stationary gang drill whereat a plurality of
drill heads drills counterbored holes for a single row. After
drilling, the indexing conveyor shifts the timber stack to drill
the next row of holes. Concurrently, the bolts are inserted and
fastened at prior set. The sequences are repeated until the mat is
fully drilled and assembled.
[0011] In one aspect of the invention there is provided an improved
apparatus for making temporary road mats of bolted construction
characterized by multiple layers of mutually perpendicular
elongated timbers having an array of vertical intersections
comprised of longitudinally spaced lateral rows, wherein said
apparatus comprises: a pair of assembly tables spaced along an
assembly line of a work floor, each of the tables having an upper
layout surface spaced vertically above the work floor and providing
a work bay therebelow, said layout surface having indicia for
orienting the discrete timbers in each layer whereby said timber
may be roughly assembled thereon into said layers with said
intersections; a gang drill assembly supported for controlled
movement in a longitudinal path along said assembly line with
respect to said pair of assembly tables, said gang drill assembly
carrying a plurality of drill units above said layout surface
aligned for drilling the lateral rows of intersection; means for
aligning said drill units at said lateral rows and for downwardly
for moving said drill units to form through holes through said
timbers at said intersections subsequent to which bolts are
inserted in into said through holes from above said layout surface
and fasteners are connected with said bolts in said work bay, the
movement of said gang drill assembly and the sequence of said
drilling being alternated between said assembly tables.
[0012] Accordingly, it is an object to provide an improved
temporary road mat having threaded fasteners releasably
interconnecting the various components.
[0013] Another object of the invention is to provide a three ply
temporary road mat fastened by carriage bolts.
[0014] A further object is to provide an improved apparatus for
assembling temporary road mats wherein rough timbers are feed on a
conveyor system through a trimming station to provide precut
timbers to a pair of spaced assembly tables for positioning into
multiple crossed layer orientation and a longitudinally
positionable multiple drill assembly alternately drills fastener
holes in the timbers at each table.
[0015] Another object is to provide an apparatus for assembling
bolted temporary road mats wherein a gang drill assembly is used to
simultaneously drill lateral rows of through holes for receiving
fasteners for interconnecting the mat components.
DESCRIPTION OF THE DRAWINGS
[0016] The above and other features and advantages of the invention
will become apparent upon reading the following written description
taken in conjunction with the accompanying drawings in which:
[0017] FIG. 1 is a side elevational view of an apparatus for the
manufacture of temporary road mats in accordance with a preferred
embodiment of the invention;
[0018] FIG. 2 is a top view of the conveyor and trimming station
for the apparatus showing the trimming of rough timbers to
length;
[0019] FIG. 3 is a top view of an assembly table and surrounding
walkway for the apparatus;
[0020] FIG. 4 is a front elevational view of the assembly table and
mobile gang drill;
[0021] FIG. 5 is a cross sectional view illustrating the drilling
of the timbers;
[0022] FIG. 6 is a cross sectional view of the timbers and carriage
bolt fasteners;
[0023] FIG. 7 is a perspective view of the temporary road mat in
accordance with one embodiment of manufacture;
[0024] FIG. 8 is a side elevational view of the temporary road mat
as shown in FIG. 7;
[0025] FIG. 9 is a top view of the temporary road mat as shown in
FIG. 7;
[0026] FIG. 10 is a front view of the temporary road mat as shown
in FIG. 7;
[0027] FIG. 11 is a front view of an apparatus for the manufacture
of temporary road mats in accordance with another embodiment of the
invention;
[0028] FIG. 12 is a side elevational view of the apparatus
illustrated in FIG. 11 taken along line 12-12 in FIG. 11;
[0029] FIG. 13 is a fragmentary cross sectional view of the
countersunk holes of the temporary road mat in the apparatus of
FIG. 11;
[0030] FIG. 14 is a fragmentary cross sectional view of the
assembled carriage bolt maintained in the countersunk holes by the
pressure plate prior to assembly; and
[0031] FIG. 15 is a top view of an embodiment of the temporary road
mat illustrating the splicing of the timbers.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0032] Referring to the drawings for the purpose of illustrating a
preferred embodiment of the invention and not for limiting same,
FIG. 1 shows an assembly apparatus 10 for the manufacture of
temporary road mats. The apparatus 10 comprises a pair of in-line
multilevel assembly lines 11. At the outer end of each line 11
rough wooden timbers 14 are delivered to a loading area 16,
transferred by conveyor 18 through trimming station 20 to produce
finished timbers 22 and unloaded at transfer area 24. The finished
timbers 22 are assembled on assembly tables 26, drilled at vertical
locations by a mobile gang drill 28, and fastened at underlying
fastener bays 29. Fully assembled mats are removed from the
assembly tables 26 by suitable material equipment such as overhead
cranes or mobile fork lifts.
[0033] Referring to FIGS. 7 through 10, a completed temporary road
mat 30, according to one embodiment, comprises three mutually
perpendicular layers of spaced finished timbers. The width and
length of the mat are generally in two foot increments and the mat
is rectangular in shape, for instance 8 feet by 12 or 16 feet.
Depending on load requirements, two layers may be sufficient and in
severe environments, greater than three layers may be preferable.
Moreover, the ends and sides may have staggered ends adapted for
interlocking assembly. Further, the top lay may be configured for
distinct vehicle tracks. For each of the above and the like, the
layers must be securely interlocked to maintain structural
integrity during use.
[0034] The mat 30 comprises a first or base layer 32 having
longitudinally extending, laterally spaced members, a second or
middle layer 34 having laterally extending, longitudinally spaced
members, and a third or top layer 36 having longitudinally
extending, uniformly laterally spaced members vertically overlying
the first layer. The assembly thus forms distinct, mutually
perpendicular layers of intersecting rows and columns in grid array
of mutually overlying intersections. Through holes, as hereinafter
described, are drilled through the overlapping members at such
intersections. Suitable fastener systems 37, as described below,
extend through the holes and bolted for mutually clamping the
layers together. In the present invention a carriage bolt is
inserted downwardly through each hole and a nut threaded thereto at
the lower surface.
[0035] As shown in FIGS. 1 and 2, timbers roughly to length are
delivered to a loading area in front of the conveyor 16. The
conveyor 16 includes a support assembly 40 having a pair of
laterally spaced guide rails 42. The guide rails 42 include
upwardly curved, arcuate entry legs 44 merging with horizontal top
legs 46. A drive chain 48 is guided on sprockets for guided
movement adjacent the guide rails. A control motor 50 is
operatively connected to the drive chain 48 for operating the chain
under manual or automatic control. Each drive chain 48 carries a
plurality of spaced transfer dogs 52 that project outwardly of the
guide rails 42. The rough timbers 14 are sequentially loaded on the
dogs 52 and transferred forwardly by the drive chain upwardly along
the entry legs 44 and inwardly along the top legs 46.
[0036] The conveyor 16 extends through the trimming station 18 and
delivers the cut timbers to the transfer area 26. The trimming
station 18, as shown in FIG. 2 includes a laterally adjustable
circular saw unit 62, a fence 64 and a transfer roll 66. The
transfer roll 66 is operatively connected to a drive unit 67 for
rotation as shown by the arrows. The saw unit 62 is mounted for
adjustable transverse movement as indicated by the arrows. As the
rough timbers 14 are carried into the trimming station 18, the
transfer roll 66 laterally shifts the timbers outwardly against the
fence 64. The circular saw unit 62 is positioned downstream beyond
the transfer roll 66 and laterally positioned to make a cross cut
on the timbers representing a selected length between the saw blade
and the fence, corresponding to the lengths in the desired mat
layer. The range of adjustment between the saw unit and the fence
is sufficient to handle sizing of the various timbers for the
manufactured mat designs.
[0037] After trimming to length, the timbers for a layer are housed
at staging area 24 prior to layout on the assembly tables. The
assembly tables 26 are carried on support frames 70 elevated above
the work floor at a sufficient height to establish a work bay 29
therebelow to enable workers to bolt the mats together as described
below. The elevation of the tables 26 is slightly above the
transfer area for providing ease of manual alignment of the members
on the assembly tables. The tables 26 are surrounded and mutually
spaced by elevated walkways 71 for permitting movement of the
workers thereabout. Depending on production rates, a single crew on
the upper level may alternate between the tables, and bolting crews
alternate between the bays. Alternatively, a single crew may
sequentially handle upper and lower level operations.
[0038] Referring to FIG. 3, the assembly tables 26 are provided a
top frame including peripheral end supports 74 and side supports 76
interconnected with interior supporting members 78. A lateral fence
80 is aligned and attached at one side support 76, and a
longitudinal fence 82 is aligned and attached at the inner end
support 74 thereby providing an alignment surface for accurately
positioning the ends of the timbers of the respective layers.
Additional pivotal fences and clamps may be provided at opposed
ends of the respective fences to mechanically position the timbers
against the prime fences 80, 82. Additionally, the lateral and
longitudinal sides are provided with spaced indicia 84 and/or
affirmative locators for accurately referencing and establishing
respective timber placement.
[0039] For assembling the bottom layer, the timbers 22 are removed
from the transfer area 24, positioned against the end fence 82, and
aligned with the indicia 84 to provide a longitudinal array of
laterally spaced timbers for the bottom layer. Concurrently
therewith, the trimming station 18 may be adjusted to trim the next
set of timbers traversing the conveyor 16 to the determined length
and in the required number for the middle layer. Alternatively, the
middle layer timbers may be sized at a separate location and
transferred to the assembly table for positioning atop the bottom
layer.
[0040] After location of the bottom layer, the ends of the middle
layer timbers are positioned against the lateral fence 80 and
aligned with the indicia 84 to provide an aligned lateral array
perpendicular to the bottom layer. Thereafter the upper set of
timbers is trimmed and aligned mutually perpendicular to the middle
layer, as described above, ready for drilling with the mobile gang
drill 28.
[0041] The mobile gang drill 28 comprises a shuttle 90 having side
support legs 92 laterally on either side of the line 10 and
interconnected by a cross member 94. The legs include a horizontal
base 93 carrying rollers 96 that are supported on longitudinal
guide rails 98 spaced on the lateral sides of the assembly tables
11. A drive motor 100 is operatively connected with the rollers 96
is operable manually or automatically to move the gang drill 28 to
controlled positions along the guide rails. A tool bar 110 is
supported by a parallel linkage 112 at the cross member 94 and
moved vertically by actuating cylinder 114 between raised and
lowered positions. A plurality of drills 116 including drill bits
118 are carried on the tool bar 110 and adjustable laterally to
register with the overlapping intersections of mat timbers for the
design being manufactured. A press plate 120 is slidably supported
at the legs 92 for vertical movement under the manual or automatic
control of actuators 122. The press plate 120 is lowered to
compressively clamp the timber layers adjacent the drills to
prevent any misalignment of the timbers during the drilling.
[0042] For the drilling sequence, the gang drill is indexed,
manually or automatically, to position the drills over the
outermost lateral row of timber intersections. Thereafter as shown
in FIG. 5, the drills are energized and the actuator 122 extended
to lower the press plate 120 to clamp the timbers. The actuator
cylinders 114 are extended to lower the tool bar 110 thereby
simultaneously drilling a lateral series of vertical holes
completely through the three layers timbers. The drills 116 are
withdrawn by the actuator cylinder 114, the press plate 120 raised
by actuator 122, and the gang drill 28 moved to the next lateral
set of intersections for repeating the foregoing drilling sequence.
The drilling continues until all holes have been drilled.
Thereafter, the drill assembly is parked intermediate the tables
prior to undertaking the drilling sequences at the other table.
[0043] Referring to FIG. 5, following the drilling on the first
row, the carriage bolts 140 are manually inserted into the drilled
holes as available and until completed. After insertion of all the
carriage bolts, a cover plate 130 is lowered onto the table over
the bolt heads 142 to maintain position thereof during fastening. A
work crew in the assembly bay 29 then fastens the nuts 144 and
washers 146 to the threaded shank 148 of the bolts 140 using
powered socket wrenches to unitize the assembly. Following
completion, the cover plate is removed and the finished mat
transferred from the table by suitable material handling equipment
such as a forklift or mobile crane.
[0044] The apparatus above described allows work crews to
continuously operate on both table. During the drilling sequence at
one table, the mats are rough assembled on the other table. During
the fastening at the first table, drilling is done at the other
table. During assembly at the first table, the fastening is
performed at the other table. In this manner, both tables are
continuously used with the workload shifting between the levels.
Moreover, the work crews may alternate between the tables at both
levels or between levels at one table thereby efficiently utilizing
both labor and machine component. It will thus be appreciated that
the two bays working in tandem are able to balance machine and
manual time content to utilize the equipment and labor in a
productive efficient manner. Compared to serial drilling and
fastening wherein about 2 mats per hour could be produced, the
inline dual table of the present invention outputs completed mats
at the rate of about 10 per hour with comparable labor content per
mat.
[0045] It will be appreciated that the foregoing apparatus may be
employed for the manufacture of differing sizes, layout and number
of intersecting timber layers. Interlocking and/or staggered mat
designs may be accommodated by table and drill layout. Further,
dedicated wheel track patterns of current design may also be
produced.
[0046] Referring to FIGS. 11 and 12, there is shown another
embodiment of the invention wherein the assembly apparatus is
provided with stationary drilling assemblies and a mobile assembly
platform. More particularly, the assembly apparatus 200 comprises a
longitudinal assembly line 202 for routing timbers 2203 in layers
onto a mobile assembly platform 204 including an indexing conveyor
206, past upper and lower drill assemblies 208, 210 respectively,
for sequentially drilling a lateral series of holes in a roughly
assembled mat 212, followed by bolting of the layers of timbers
into compressive engagement to form a finished mat in upper
assembly area 214 and lower assembly area 216.
[0047] The timbers 203 are transferred to the assembly platform by
conveyor and trimming stations including end station 220, and side
stations 222, and 224. The stations 220, 222, and 224 may be the
same as the conveyor 18 and trimming station 20 described with
reference to the first embodiment. The timbers may be inventoried
at storage areas at the ends thereof or manually transferred as
available to the assembly table.
[0048] The apparatus 200 includes an elevated platform 230 mounted
on a base 231, such as a plant floor. The platform 230 extends
along the assembly line 202 and supports the indexing conveyor 206.
The drill assemblies 208, 210 are carried by a support frame 234 at
about the center of the platform 230. The support frame 234
includes a pair of laterally spaced legs 236 attached to the base
231 and interconnected by cross arm 238.
[0049] The apparatus 200 provides the capability of assembling
extended length platforms and accordingly the lateral timbers
comprise the top and bottom layers 32, 36 and feed from the side
stations 222, 224, with the longitudinal timbers comprising the
middle layer 34 and supplied from the end station 220.
[0050] The indexing conveyor206 includes a pair of laterally spaced
motor driven drive chains 240 driven by motor 241 and extending
longitudinally along the frame 234. The drive chains 240 include
projecting lugs 242 engagable with the base layer timbers. By
appropriate automatic or manual control, the conveyor 206 is
intermittently operated to index successive lateral timbers at the
drilling assemblies whereat the vertical fastener profile is
formed.
[0051] The upper gang drill assembly 208 is supported on the frame
and is substantially the same as the drill assembly in the first
embodiment and reference may be made thereto for details thereof.
The lower gang drill assembly 210 comprises a laterally spaced
series of drills 244 supported on a cross bar 246 carried on the
legs 236 of the frame 234 for movement by a hydraulic actuator 248
between the illustrated normal lowered position to a raised
drilling position.
[0052] To provide for recessing on the fastener to avoid surface
projections on the top and bottom surfaces of the mat, as shown in
FIG. 14, the drilled fastener profile includes a through hole 250,
an upper counterbore 252 for the head of the bolt, and a lower
counterbore 254 for the nut of the fastener.
[0053] The profile is formed by a drill bit on the upper drills
comprising a main drill bit for forming the through hole 250 and a
counterbore bit for forming the upper counterbore 252, and a drill
bit on the lower drills 246 comprising a pilot drill and a
counterbore bit for forming the lower counterbore 252.
[0054] In operation, with a lateral row of timber intersections
indexed at the drill assemblies, the actuator 248 is extended to
raise the lower drill assembly 210 for drilling the lower
counterbores. Thereafter the upper drill assembly 206 is lowered
for drilling the through hole and upper counterbores. The sequence
is repeated for the remaining lateral rolls of the mat.
[0055] After the first row of profiles is formed and the mat
indexed, the carriage bolts are inserted. This provides for low
stress assembly inasmuch as the holes are coaxial at drilling and
the short transfer area presenting little opportunity for timber
shifting. After assembly of the first row, the alignment becomes
increasingly stable thereby allowing the close sliding fit between
the fastener and holes. To prevent the upward movement of the
carriage bolts during attachment of the nuts, a slightly downwardly
inclined plate 250 is supported above the table and timbers,
downstream of the bolt assembly area. In the lower bay 260 below
the table, the nuts are assembled on the bolts to create the
composite mat. Upon completion, the composite mat is transferred
from the line by appropriate material handling equipment. Depending
on the front length of the indexing conveyor, initial assembly may
commence on another mat while the preceding mat is finishing
drilling and assembly.
[0056] The three layer composite mats possess substantially
improved bending and torsional strength in comparison with
conventional nailed mat constructions. Such strength enables
assembly used sliced timbers. As shown in FIG. 15, the top layer
may comprise columns having spliced timbers 270, 271 thereby
permitted the use of easier to obtain and cost effective timber
lengths. The spliced construction may be used for all or a portion
thereof. In such a spliced construction, it is desireable to
stagger the spliced joints. Similar techniques may be used for the
middle row 34 using spliced timbers 272, 273, and bottom layer 32
using spliced timbers 274.
[0057] Having thus described a presently preferred embodiment of
the present invention, it will now be appreciated that the objects
of the invention have been fully achieved, and it will be
understood by those skilled in the art that many changes in
construction and widely differing embodiments and applications of
the invention will suggest themselves without departing from the
sprit and scope of the present invention. The disclosures and
description herein are intended to be illustrative and are not in
any sense limiting of the invention, which is defined solely in
accordance with the following claims.
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